Fetal Monitoring Flashcards
What are methods of fetal monitoring in labour?
Intermittent auscultation Continuous cardiotocography (CTG)
How does intermittent auscultation work? How often?
Doppler US for a full minute after a contraction in low risk women
Every 15min in 1st stage
Every 5min throughout second stage
If abnormality - start CTG
How is CTG monitoring carried out?
Abdominal probe (US) or a fetal scalp electrode Latter is useful if there is doubt about source of heartbeat, poor contact of abdominal probe, obesity and very mobile women but requires rupture of membranes
One transducer records fetal heart rate using US
Other monitors contraction of uterus by measuring tension of abdominal wall - indicates intrauterine pressure
What are indications for electronic fetal monitoring?
Induction of labour Post-maturity (>42 weeks) Previous LSCS Maternal cardiac problems Pre-eclampsia or hypertension Prolonged rupture of membranes > 24h Prematurity < 37 weeks DM Antepartum or intrapartum haemorrhage Small for gestational age Oligohydramnios Abnormal umbilical artery Doppler Multiple preganncy Meconium stained liquor Abnormal lie Oxytocin augmentation Epidural Pyrexia Abnormality on intermittent auscultation
How do you describe CTG?
DR C BraVADO
Define risk Contractions - per 10 minutes BRA - Baseline rate V - variability Accelerations Decelerations Overall impression - normal, non-reassuring, abnormal
How do you define risk? What are indications of high risk?
Assess if pregnancy is high or low risk
Maternal medical illness:
Gestational diabetes
Hypertension
Asthma
Obstetric complications: Multiple gestation Post-date gestation Previous C-section IUGR PROM Congenital malformations Oxytocin induction/augmentation Pre-eclampsia
Smoking
Drug abuse
How do you work out number of contractions?
Each big square is equal to one minute
- count the number of peaks in 10 big squares
If 2 - 2in 10
Assess:
Duration of contraction
Intensity of contraction - assess with palpation
How do you calculate baseline rate
Average level of foetal heart rate when any accelerations or decelerations have been excluded
Appears as straight-ish line between other features
Look at CTG and assess what average heart rate has been over last 10 minutes
What is normal fetal heart baseline rate?
100-160
What is fetal tachycardia? Causes?
> 160bpm
Fetal hypoxia Chorioamnionitis Hyperthyroidism Fetal or maternal anaemia Fetal tachyarrhythmia
What is fetal bradycardia? Causes?
Baseline rate < 100bpm for 3 minutes or more
Postdate gestation
Occipitoposterior or transverse
What is severe prolonged bradycardia? Causes?
Less than 80 bpm for more than 3 minutes
Prolonged cord compression Cord prolpase Epidural and spinal Maternal seizures Rapid fetal descent
What is variability?
Variation of the fetal heart rate from one beat to next
Indicator of how healthy fetus is - healthy fetus will consistently be adapting its heart rate in response to changes to environment
What is normal variability?
5-25bpm
How do you calculate variability?
Look at how much peaks and troughs of heart rate deviate from baseline rate
How is variability categorised?
Reassuring: 5-25bpm
Non-reassuring:
< 5 bpm for 30-50min
more than 25 bpm for 15-25 mins
Abnormal:
<5 bpm for > 50 minutes
>25 for more than 25 minutes
Sinusoidal
What re causes of reduced variability?
Fetal sleeping (no longer than 40 mins) Fetal acidosis due to hypoxia Fetal tachycardia Drugs - opiates, benzodiazepines, magnesium sulphate Prematurity < 28 weeks Congenital heart abnormalities
What are accelerations?
Upward spike of >15 bpm for >15 seconds
Reassuring feature
Commonly occur when fetus is moving
What are decelerations?
Downward spike of baseline fetal heart rate >15 bpm for >15 seconds
Reduction in heart rate to reduce myocardial demand
What are early decelerations? What causes them?
Start when uterine contraction begins and recover when uterine contractions stops
Due to increased fetal intracranial pressure causing increased vagal tone
Physiological
Seen in breech presentation and in second stage of labour
What are variable decelerations? When is it concerning?
Rapid fall in baseline fetal heart rate with a variable recover phase
Variable in duration
Most often seen during labour and in oligohydramnios
Concerning if: >60 seconds Reduced baseline variability within deceleration Failure to return to baseline Bisphasic W shape No shouldering
What are causes of variable deceleration?
Umbilical cord compression
Umbilical vein is often occluded first causing an acceleration
Then umbilical artery is occluded causing subsequent rapid deceleration
When pressure on the cord is reduced another acceleration occurs then the baseline rate returns
Acceleration before and variable deceleration are known as shoulders
Shoulders indicate fetus is not yet hypoxic and is adapting to reduced blood flow
Variable decelerations without shoulders suggests hypoxia
What are late decelerations? Causes?
Begin at the peak of uterine contraction and recover after contraction ends
Insufficeint blood flow to the uterus and placenta
Hypoxia and acidosis of fetus
Maternal hypotension
Pre-eclampsia
Uterine hyperstimulation
What should be done if late decelerations?
Fetal blood sampling for pH
–> Emergency C-section if acidotic
